Funds are being requested to purchase a NanoSPECT small-animal SPECT (single-photon emission computed tomography) and CT (transmission computed tomography) scanner (Bioscan, Washington, DC) for non-invasively and longitudinally monitoring cancer and other disease processes, trafficking of cancer, immune, and stem cells, cellular responses to therapy and other interventions, genetic pathway expression, and tumor targeting and biodistribution of new radio diagnostic and radio therapeutic agents in small-animal (i.e. mouse and rat) models. This state-of-the-art instrument, to be installed in our existing Small-Animal Imaging Core Facility, will be a critical, broadly used addition to the pre-clinical and translational oncology research program at Memorial Sloan-Kettering Cancer Center (MSKCC). Like our existing (but technically limited and outdated) microSPECT-microCT system, the X- SPECT, the NanoSPECT will play a critical role in the development of novel radio diagnostic and radio therapeutic agents (including "anti-tumor" antibodies and other immune constructs), gene imaging (i.e. reporter gene) systems and in vivo imaging of various cellular and molecular-genetic processes critical to our understanding of the natural history of cancer and its response to various therapies. Funds for a new, far more functional microSPECT-microCT system, the NanoSPECT, are therefore urgently requested to enhance and expand our in vivo radionuclide imaging capabilities and to provide more quantitatively reliable three-dimensional (tomographic) in vivo radionuclide imaging capability. Among the critical advantages of the NanoSPECT over our outdated X-SPECT are: (1) substantially higher sensitivity, yielding higher quality, more quantitatively accurate images in shorter imaging times;(2) the capability of performing whole-body ultra-high-resolution pinhole SPECT studies, providing whole-body biodistribution data and recognizable anatomic information in a single study;and (3) the capability to image high-energy single- photon emitters such as iodine-131 (131I), a widely used and important "therapeutic" radionuclide not image-able with the X-SPECT. In addition to numerous funded projects with scientific plans in place to use the NanoSPECT, our Facility and our Center have well-established technical and scientific expertise to fully and immediately utilize this instrument upon its installation and a highly efficient administrative and financial infrastructure in place to support and maintain this instrument and its effective use long-term.